Problems with load balancing cluster on GFS

[Klaus Steinberger]

> I'm seeing some weird behaviour with the pop3 daemon on a GFS HA
> cluster with load balancing.

I would not advise running cyrus-imapd on top of GFS. GFS is even with  
the best tuning possible very slow regarding small files (the typical  
load type of a cyrus-imapd). GFS runs into heavy locking with that  
type of load. So don't do it.

What I'm currently doing:

I run on top of a RH Cluster (using Scientific Linux) virtual machines  
with XEN. rgmanager handles very well the failover of XEN instances.  
So I just run one VM with a cyrus-imapd. (this cluster handles all of  
my DMZ servers, e.g. it runs VM's for static webpages, typo3 and so  
on, currently around 15 VM's). The cluster is a 3 node setup with an  
SAN Storage.

A Logical Volume is exported to the XEN VM, inside this Volume i  
create again a Volume Group. A Logical Volume is created for  
/var/spool/imap, which is formated just as ext3. There is no cluster  
locking necessary as just one virtual machine accesses this Volume. As  
the Volume Group is inside the VM, I can use Snapshots also (not  
possible on clvm).

  Current size of my Imap Server is 2500 users and currently 250 GByte  
of Mailboxes used (growing and growing).

I don't see how to avoid a murder setup if you need more than one  
machine running cyrus-imapd in parallel.

Sincerly,
Klaus

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